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11.6.1 Before You Start
Before configuring multicast two-node hot backup, familiarize yourself with the usage scenario,
complete the pre-configuration tasks, and obtain the required data.
Applicable Environment
IPTV applications become popular and IPTV services are transmitted in real time. Users are
sensitive to IPTV service stability, which imposes high reliability requirements on operator
networks. IPTV is deployed using the Protocol Independent Multicast (PIM) and Internet Group
Management Protocol (IGMP). PIM directs multicast services to multicast group members that
send requests. IGMP transmits multicast services only to terminals that order programs.
The network as shown in
transmits IPTV services. Two routers that connect IP core
devices to a Layer 2 access network and devices on the IP core network run PIM; Layer 2 access
network devices run IGMP. Two routers deployed at the edge of the IP core network provide
redundancy. Interfaces connecting the two routers to the access network are enabled with PIM
and BFD. A designated router (DR) and a backup designated router (BDR) are elected between
the routers. The DR sends copies of a program to terminals. If the DR fails, the BDR becomes
the DR and sends copies of multicast traffic downstream. BFD rapidly detects faults and allows
the BDR to rapidly take over multicast traffic.
Existing IPTV terminals support DHCP and PPPoE access to routers.
If IPTV terminals run PPPoE, multicast duplication points are BRASs. A BRAS sets up a point-
to-point PPPoE session with a terminal. Network elements (NEs) on the link between the BRAS
and terminal do not sense the presence of the session. BRASs function as a DR and a BDR. If
BRAS1 fails, BRAS2 that does not store PPP session information is unable to transmit IPTV
services. The terminal re-dials up and is connected to BRAS2 to restore the IPTV services. This
process results in a long service interruption. Multicast hot backup allows a PPPoE IPTV
terminal to smoothly restore IPTV services without re-dialing up or changing a channel if a
BRAS fails.
HUAWEI NetEngine80E/40E Router
Configuration Guide - Reliability
11 Multi-node Backup Configuration
Issue 02 (2014-09-30)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
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